1. Field of the Invention
The present invention relates generally to a mobile telecommunication terminal, and more particularly to a universal asynchronous receiver/transmitter circuit for a mobile telecommunication terminal.
2. Discussion of the Related Art
A related art mobile telecommunication terminal is coupled to a connection device, such as a 19-pin receptacle (receptacle), through a hands-free device or a data communication cable. The data communication cable connects a communication device (or a terminal) to a computer. The communication device connected to the computer may then serve as a wireless modem. Using such a connection, a user can communicate through wireless internet or wireless data communication.
FIG. 1 is a block diagram showing an example of a universal asynchronous receiver/transmitter circuit in a related art mobile telecommunication terminal.
Referring to FIG. 1, a mobile station modem (MSM) 110 is connected to a 19-pin receptacle 120. FIG. 1 shows signal processing between a hands-free functional part 111 and a first universal asynchronous receiver/transmitter (UART1) 112 of the mobile station modem 110 and the 19-pin receptacle 120.
The 19 pins of the receptacle 120 include 6 pins allotted to processing functions related to the hands-free mode. The processing functions related to the hands-free mode may include receiving hands-free audio signals (PCM RX), transmitting hands-free audio signals (PCM TX), a hands-free pulse code modulation clock (PCM CLOCK), a hands-free pulse code modulation synchronizing signal (PCM SYNC), a hands-free ring terminal (RING), and a hands-free mode identifying terminal (HANDS-FREE MODE). Furthermore, 7 pins are allotted for processing functions related to data communication. The processing functions related to data communication include receiving data (RXD), transmitting data (TXD), a ring indicator (RI), a data carrier detect (DCD), a ready for receiving (RFR), a clear to send (CTS), and a data terminal ready (DTR). Additionally, 6 pins are allotted terminals for performance of other functions, such as, supplying device power (POWER (4.2V)), supplying battery charging power (POWER (4.2V)), grounding power (POWER GROUND), which requires 3 terminals, and identifying external power (equal to or less than 3.3V).
To accommodate additional functions newly developed for mobile telecommunication terminals, simultaneous use of two universal asynchronous receiver/transmitters (UART) is desirable. However, if a related art 19-pin receptacle is used, two UARTs may not be used simultaneously because the 19-pin receptacle does not have an adequate number of pins to accommodate simultaneous use of both UARTs.